The present invention relates generally to wireless communication systems and, more particularly, to systems that provide continuity for SIPTO (Selective Internet Protocol Traffic Offload).
Wireless communication systems, such as the 3rd Generation system (3G) are well known. 3G has generally been developed to support macro-cell mobile phone communications. Such macro-cells use high power base stations (referred to as NodeBs) to communicate with wireless communication units or ‘user equipments’ (UE) within a relatively large geographical coverage area. Typically, a UE communicates with a Core Network (CN) of the 3G system via a Radio Network Subsystem (RNS). A wireless communication system typically has many RNS, each having one or more cells to which UEs may attach, and thereby connect to the network. UEs are also capable of relocating from one cell's coverage area to that of another, neighbouring cell in a process known as hand-over. Relocation may be initiated because the user of the UE moves out of a source cell coverage area and into a target, neighbour cell's area. Alternatively, the UE may relocate to another cell in order to access a service that is not available in its current cell.
Communications systems and networks are developing towards a broadband and mobile system. The 3G Partnership Project has proposed a Long Term Evolution (LTE) solution, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network, (E-UTRAN), for a mobile access network, and a System Architecture Evolution (SAE) solution, namely, an Evolved Packet Core (EPC), for a mobile core network. An evolved packet system (EPS) network provides only packet switching (PS) domain data access so a voice service may be provided by a 3G Radio Access Network (RAN) and circuit switched (CS) domain network. UEs can access the EPC through the E-UTRAN. Generally, the EPC is responsible for switching and routing data to and from the Internet. Lower power (and therefore smaller coverage area) cells are a recent development within the field of wireless cellular communication systems. Such small cells are effectively communication coverage areas supported by low power base stations. A low power base station that supports a small cell is often referred to as a Home Node B (HNB) in 3G parlance or an Evolved Home Node B (HeNB) in LTE parlance. These small cells are intended to augment the wide area macro network and support communications to UEs in a restricted, for example, indoor environment. An additional benefit of small cells is that they can offload traffic from the macro network, thereby freeing up valuable macro network resources. Thus a HeNB may provide users with access to LTE services over small service areas, such as homes or small offices. The HeNB may be intended to connect to an operators' core network by using, for example, public Internet connections. This may be particularly useful in areas where LTE may not have been deployed and/or legacy 3GPP radio access technology (RAT) coverage may already exist. This may also be useful in areas where LTE coverage may be faint or non-existent for radio transmission problems that occur, for example, while in an underground metro (subway) or a shopping mall.
LTE networks are becoming more and more congested. One known solution of reducing traffic in LTE networks is the use of the so-called Selective IP (Internet Protocol) Traffic Offload (SIPTO). SIPTO is a method of offloading traffic from a core network to a defined IP network. One known system includes a local gateway (L-GW) that may be located close to a HeNB and configured to perform IP traffic offload based on an IP address destination. IP traffic may then go through the L-GW to the Internet via the user's home network rather than through the Operator's Core Network. Local IP Access (LIPA) is a method for providing access for IP-capable UEs that are connected via an HeNB for example, to other IP capable entities in the same residential or enterprise IP network. Traffic for LIPA typically does not traverse the operator's network except for accessing particular information at the HeNB. These methods have their limitations. For example, SIPTO does not specify how lawful interception of traffic may be performed. Further, UE mobility, particularly maintenance of a session when roaming, is not specified. Therefore it would be advantageous to provide a system for reducing core network traffic without the limitations of the known systems.